Calculated according to the following formula: interest of loan A+interest of loan B = 8.42 (interest = principal × interest rate× time).

12℅ⅹ+(68-ⅹ)× 13℅=8.42

12℅ⅹ+8.84- 13℅ⅹ=8.42

8.84- 1℅ⅹ=8.42

1℅ⅹ=0.42

X = 42 68-42 = 26 (ten thousand yuan)

A: The amounts of the two loans are 420,000 yuan and 260,000 yuan respectively.

Question 4: Bank deposit interest = after-tax interest+interest tax. Individuals can only get after-tax interest, and interest tax is a part of the country. The interest tax rate seems to be 5% (if not, please refer to your textbook), and it is calculated according to the formula of after-tax interest.

Principal × interest rate × time ×( 1-5℅)= after-tax interest (assuming interest rate is X).

10000ⅹ×2×( 1-5℅)= 10520- 10000

19000ⅹ=520

ⅹ≈2.74℅

Exercise 6.4

1、3x 4x 3x+x+4x= 10

2. The height of the Oriental Pearl = 40 ÷ (23-21) × 23 = 460m.

The height of Jinmao Tower = 40 ÷ (23-21) × 21= 420m (or 460-40 = 420m).

3. Xiaoli's age = 54(7+2)×2 = 12 years old.

Dad's age = 54(7+2)×7 = 42 (or 54- 12=42).